March, 1918] .1 Lecher System — Experiniental 



159 



ively using the figures of column 2o instead of column 20. 

 In column 21 the first figure in each of the first three sets 

 is arbitrarily taken equal to the first figure in column 18, 

 the first figure in column 22 being necessarily equal to 

 that in column 19. The justification for this may be seen 

 in Figure 7 where columns 18 and 21 are plotted against 

 the frequency number for the first five sets, column 21 

 being represented b}^ the dotted lines. For 7/ = 8 the agree- 



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